OSSOS. IX. Two Objects in Neptune's 9:1 Resonance-Implications for Resonance Sticking in the Scattering Population

• Published in: The Astronomical journal 2018-06, Vol.155 (6), p.260
• Main Authors: Volk, Kathryn, Murray-Clay, Ruth A., Gladman, Brett J., Lawler, Samantha M., Yu, Tze Yeung Mathew, Alexandersen, Mike, Bannister, Michele T., Chen, Ying-Tung, Dawson, Rebekah I., Greenstreet, Sarah, Gwyn, Stephen D. J., Kavelaars, J. J., Lin, Hsing Wen, Lykawka, Patryk Sofia, Petit, Jean-Marc
• Format: Article
• Language: English
• Subjects: Astronomy; Astrophysics; ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ASYMMETRY; Axis movements; Computer simulation; COMPUTERIZED SIMULATION; HYPOTHESIS; Kuiper belt; Kuiper belt: general; Libration; Neptune; Object recognition; Orbital resonances (celestial mechanics); Outer solar system; Physics; Polls & surveys; Population; RESONANCE; Resonance scattering; Solar system; SOLAR SYSTEM EVOLUTION; SYMMETRY
• ISSN: 0004-6256; 1538-3881; 1538-3881
• DOI: 10.3847/1538-3881/aac268

We discuss the detection in the Outer Solar System Origins Survey (OSSOS) of two objects in Neptune's distant 9:1 mean motion resonance at semimajor axis a 130 au. Both objects are securely resonant on 10 Myr timescales, with one securely in the 9:1 resonance's leading asymmetric libration island and the other in either the symmetric or trailing asymmetric island. These objects are the largest semimajor axis objects with secure resonant classifications, and their detection in a carefully characterized survey allows for the first robust resonance population estimate beyond 100 au. The detection of these objects implies a 9:1 resonance population of 1.1 × 104 objects with Hr < 8.66 (D 100 km) on similar orbits (95% confidence range of ∼(0.4-3) × 104). Integrations over 4 Gyr of an ensemble of clones spanning these objects' orbit-fit uncertainties reveal that they both have median resonance occupation timescales of ∼1 Gyr. These timescales are consistent with the hypothesis that these objects originate in the scattering population but became transiently stuck to Neptune's 9:1 resonance within the last ∼1 Gyr of solar system evolution. Based on simulations of a model of the current scattering population, we estimate the expected resonance sticking population in the 9:1 resonance to be 1000-4500 objects with Hr < 8.66; this is marginally consistent with the OSSOS 9:1 population estimate. We conclude that resonance sticking is a plausible explanation for the observed 9:1 population, but we also discuss the possibility of a primordial 9:1 population, which would have interesting implications for the Kuiper Belt's dynamical history.